This project aims at the further elucidation of the role of 'neuropeptides' derived from neural and non-neural cells in the regulation of immune processes in the blattarian insect Leucophaea maderae. The effects of substances resembling corticotropin (ACTH), melanocyte-stimulating hormone (MSH) and prolactin, whose presence in the insect's neuroendocrine system has been demonstrated immunocytochemically, will be given special attention. Attempts win be made to identify the same or closely related endogenous molecules in the hemolymph by radioimmunoassay. Their participation in cell-mediated autoregulatory immune processes will be determined by their effect on cellular conformation and motility observed in slide tests. Evidence suggesting the operation of neuroendocrine control mechanisms governing immunocyte function will be sought by subjecting the insects to various stressful stimuli and recording effects on immunocyte activation comparable to those brought about by exogenous opioid peptides. The blockage of such a response by the administration of the opioid antagonist naloxone would strengthen the conclusion that endogenous neuropeptides released by neuroendocrine structures alert the insect's defense system. The recent discovery that Periplaneta, a close relative of Leucophaea, is capable of a specific vertebrate-like anamnestic response to toxoid-treatment (Dunn, 1990) opens the way for comparable experiments in Leucophaea and for the investigation of the possible participation of neuropeptides in vertebrate-type humoral immune processes in this invertebrate. Immunocytochemical studies on the presence of selected neuropeptides in the neuroendocrine system of Leucophaea will be continued, aiming primarily at the further characterization of signal molecules involved in immunoregulation.